Modern technologies develop prosperously. Information products are introduced continuously to satisfy varied demands of numerous people. Most of early displays are cathode ray tubes (CRTs). However, their size is huge and their power consumption is great. In addition, the radiation they produced may endanger the health of long-term users. Thereby, current displays in the market are gradually replaced by liquid crystal displays (LCDs). LCDs have the characteristics of lightness, thinness, shortness, and smallness. Besides, they also have the advantages of low radiation and power consumption. Hence, they have become the mainstream of the market.
LCDs display images by controlling the light transmittance of liquid-crystal cells according to data signals. Because active-matrix LCDs adopt active control switches, the LCDs of this sort own advantages in displaying motion pictures. Thin-film transistors (TFTs) are switches mainly used in active-matrix LCDs.
FIG. 1 shows a schematic diagram of the driving system for an LCD according to the prior art. As shown in the figure, the driving system comprises a display panel 10′, a scan driving circuit 12′, a data driving circuit 14′, a timing control circuit 16′, and a circuit for producing reference voltages 18′. The display panel 10′ is used for displaying images. The scan driving circuit 12′ is used for producing and transmitting a scan signal to the display panel 10′ for driving a thin-film transistor (TFT) of the display panel 10′. The data driving circuit 14′ is used for producing and transmitting a data signal to the display panel 10′ for displaying the images. The timing control circuit 16′ produces a timing control signal, and transmitting the timing control signal to the scan driving circuit 12′ and the data driving circuit 14′, respectively, for controlling the scan driving circuit 12′ and the data driving circuit 14′ to transmit the scan signal and data signal to the display panel 10′, respectively, and for displaying the images. In addition, the circuit for producing reference voltages 18′ produces a reference voltage and transmits the reference voltage to the data driving circuit 14′ for making the data driving circuit 14′ to produce the data signal according to the timing control signal and the reference voltage.
FIG. 2 shows a schematic diagram of a circuit for producing reference voltages according to the prior art. If the digital display data corresponding to RGB is comprised by, for example, 6 bits, the circuit for producing reference voltages 18′ can output 64 analog voltages V0˜V63 corresponding to 26=64 grayscales. The circuit for producing reference voltage 18′ is comprised by resistive voltage division circuit including resistors R0˜R7 connected in series. Each of the resistors R0˜R7 is further comprised by 8 resistors connected in series. As shown in FIG. 3, the 8 resistors R01˜R08 are connected in series to form the resistor R0. Other resistors R1˜R7 are formed similarly. Thereby, the circuit for producing reference voltages 18′ is comprised by 64 resistors and produces voltages V0˜V63.
However, because 64 resistors are needed to produce 64 different voltage levels, the area of the circuit for producing reference voltages 18′ is increased, and hence increasing the area of the display. Besides, in order to reduce the area of the circuit for producing reference voltages 18′, resistors with larger resistance have to be used, which will affect the driving capability of the data driving circuit 14′. Moreover, when the data driving circuit 14′ drives the display panel 10′ via the resistors, a large amount of power will be consumed on the resistors, and thus wasting power of the display.
Accordingly, the present invention provides a novel driving circuit for a display panel, which can reduce the amount of resistors used without sacrificing the driving capability of the data driving circuit 14′. Thereby, the area of the display can be reduced, and the power of the display can be saved.